The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of IC processing and manufacturing. For these advances to be realized, similar developments in IC processing and manufacturing are needed. For example, the need to perform higher resolution lithography processes grows.
Pellicles are used in lithography processes to protect a photomask from damage or contamination from particles. However, as pellicles age (for example through lithography exposure), they may become brittle or lose its elasticity. The optimal, thermal, and/or mechanical properties of pellicles also become worse as pellicles age. Existing methods of determining pellicle aging have not been entirely satisfactory. In addition, existing methods of removing contaminant particles from pellicles may damage the pellicle as well.
Therefore, an effective method and apparatus are needed to determine pellicle aging and to remove contaminant particles from the pellicle.